University at Buffalo

Behavioral Medicine Clinic


IBS: Making the Diagnosis

The nature of IBS symptoms can be a diagnostic challenge for even the most skilled physician because IBS symptoms can mimic symptoms of organic GI diseases. As a result, patients with IBS often undergo extensive work–ups before obtaining a correct diagnosis. This produces an undesirable uncertainty, anxiety, and demand for further tests. Although each of these diagnostic tests have utility in evaluating certain GI problems, arriving at a positive IBS diagnosis does not necessarily require extensive diagnostic testing. At present IBS has no reliable biomarkers and no tests can positively diagnose IBS.

Studies have shown that patients with suspected IBS are no more likely than those in the general population to have IBD, colorectal cancer, or thyroid dysfunction. While rates for celiac disease and lactose malabsorption are higher in IBS patients than in the general population, there are important symptom differences that can facilitate accurate diagnosis. Unlike patients with lactose intolerance or celiac disease, for example, IBS patients report that the onset of pain is associated with changes in the frequency and/or consistency of bowel function.

Rome III Diagnostic Criteria

Establishing a diagnosis of IBS is made on the basis of characteristic symptoms. A positive diagnosis early in the process of consultation is good for the patient because it facilitates the acquisition of self management skills which is more difficult while the diagnosis is unknown. Current diagnostic criteria for IBS (called Rome III criteria) characterize patients with IBS as having recurrent abdominal discomfort* or pain at least three days per month in the last three months associated with two or more of the following:

  1. Pain or discomfort improves with defecation
  2. The onset of pain or discomfort is associated with a change in stool frequency
  3. The onset of pain or discomfort is associated with a change in stool appearance or form
Recent US guidelines advocate a simpler definition for IBS: “abdominal pain or discomfort that occurs in associated with altered bowel habits over a period of at least 3 months”.

* Discomfort means an uncomfortable sensation not described as pain

Source: Brandt LJ, Chey WD, Foxx–Orenstein AE, Schiller LR, Schoenfeld PS, Spiegel BM, Talley NJ, Quigley EM. An evidence-based position statement on the management of irritable bowel syndrome. Am J Gastroenterol 2009;104 Suppl 1:S1–35. 1.
Longstreth GF, Thompson WG, Chey WD, Houghton LA, Mearin F, Spiller RC. Functional bowel disorders. Gastroenterology 2006;130:1480–91.

Bristol Stool Form

IBS researchers developed a seven point visual scale for assessing the consistency or form of stools. It is called the Bristol Stool Form Scale, or BSFS for short. It shows a range of bowel movements ranging from diarrhea (Type 6 and 7) to constipation (Type 1 or 2). The stool form types of the BSFS correlate with intestinal transit time. Asking patients to describe the typical consistency of their bowel movement can be useful in determining the most severe or bothersome bowel symptom around which treatment is structured.

Bristol Stool Form Scale

IBS Subtypes

Patients with constipation predominant IBS (IBS-C) experience the following:

  • hard or lumpy stools (Type 1 or 2 on the BSFS) in more than 25 percent of bowel movements and
  • loose (mushy) or watery stools (Type 6 or 7 on the BSFS) in less than 25 percent of bowel movements
Patients with diarrhea predominant IBS (IBS–Diarrhea) experience the following:
  • loose (mushy) or watery stools (Type 6 or 7 on the BSFS) in more than 25 percent of bowel movements and
  • hard or lumpy stools (Type 1 or 2 on the BSFS) in less than 25 percent of bowel movements
Patients with mixed IBS (IBS–M) experience the following:
  • hard or lumpy stool in at least 25 percent of bowel movements and
  • loose (mushy) or watery stools in at least 25 percent of bowel movements

Managing the Difficult IBS Patient

Because there is no satisfactory medical treatment for IBS, many heath care professions find IBS a difficult problem to manage. At the same time IBS patients are occasionally frustrated by previous encounters with health care professionals and are reluctant to seek treatment options that can help. As a medical professional, you can play a crucial role in guiding these people to seek evidence–based treatment for symptoms. Here are some suggestions for getting the most out of your encounters with patients.

Acknowledge seriousness.

Often, IBS sufferers find that others trivialize this condition. As a trusted health care professional to whom your patients are looking for expert guidance, your recognition that IBS is real and serious can persuade patients to seek treatment and begin returning their lives to normal. Your advice can go a long way in helping them, and you, manage their symptoms more effectively.

In offering reassure to your patients, it is important to avoid statements that may be interpreted as dismissive: “It’s nothing to worry about,” or “It’s just stress,” for example. Patients need to hear words that reflect an understanding of the legitimacy of the disorder regardless of the lack of underlying organicity. Many professionals who have treated IBS have found patients receptive to the following explanation

“You have a condition called Irritable Bowel Syndrome that can improve with proper treatment. Without addressing the factors that aggravate IBS or the way it affects your life, it can take a toll on you. This would be unfortunate because there are professionals trained to help IBS sufferers gain control over symptoms even when medications and dietary changes don’t provide adequate relief. In fact, behavioral treatments are some of the most effective IBS treatments available”

Also, some people feel their condition is too embarrassing to bring to a health care professional’s attention and have heard some health care providers and family and friends tell them that it is “all in their heads.” By telling them that the disorder has both behavioral and biological components just like other “real” medical problems like hypertension, asthma, or arthritis, you can reassure your patients that there are many facets of IBS and its symptoms that can be helped.

Knowing more about their IBS disorder can help people overcome their fear, embarrassment, or skepticism about treatment. For example, your patients may benefit from hearing that millions of people have IBS disorder – in fact, one out of five people has, or will have it. Point out that treatment can make a significant difference in their lives in just weeks or months. Engage the patient as an active, fully informed participant in the treatment planning process.

Finally, encourage your patients to seek evidence based treatment about IBS when medications or dietary changes aren’t enough. As recently described in the New England Journal of Medicine (Mayer, 2008), the behavioral self–management treatment developed at UB is one of the few empirically supported treatments for IBS. Behavioral treatments combine a variety of behavioral change strategies based on a biopsychosocial approach. Behavioral approaches emphasize teaching patients tools and strategies for controlling IBS symptom. If your patient qualifies for one of our research studies, they may benefit from state of the art treatment typically offered at no cost. Eligible patients receive financial compensation for their time and need not suspend ongoing medical treatments during trial participation. For help managing more complex IBS patients, contact the IBS Outcome Study at the BMC at 716–898–4458.


Mayer EA. Clinical practice. Irritable bowel syndrome. N Engl J Med 2008;358:1692–9.